In recent years, a plurality of Web sites, systems, and services cooperate to one another to provide a service and allow seamless access to such sites, systems, and services. In accessing such sites, a system called single sign-on (which may be referred to also as “single sign-in,” “single log-on,” or “single log-in” and will hereinafter be collectively referred to as “SSO” (Signal Sign-On) in some cases) may be used such that authentication can be performed by use of a single user ID in access to each Web site and the like.
Various techniques relating to the SSO have been proposed. For example, Japanese Patent Application Laid-Open Publication No. 2013-152757 (Patent Document 1) describes a technique by which user IDs in a plurality of systems are associated with one another by use of user ID mapping between the systems to achieve the SSO between the systems. According to this technique, a first, system acquires user ID information on the first system, and according to an intersystem user ID mapping table, acquires ID information on a second system from the user ID information, and then, transmits the acquired ID information to the second system. Upon succeeding in authentication of a user, the second system automatically permits the user to log on.